Needle protection devices, also known as needle guards, are well known. Various types exist, including rigid needle guards that have an inner body made of flexible material and an outer body made of rigid material. The inner body guarantees sealing both of the orifice of the needle and of the injection device, generally the syringe body, while the outer body serves to fasten and maintain the needle guard on the injection device until said device is used. Documents EP 1 208 861 and FR 2 777 787 describe in particular needle protection devices of that type. Documents WO 01/54758, WO 88/03816, EP 1 759 729, U.S. Pat. No. 5,746,733, and WO 02/11799 describe other prior-art devices.
Those devices may present certain drawbacks. Thus, it is not possible to prevent the needle guard from being removed inadvertently or accidentally prior to using its associated injection device, which could result in a risk of contamination of the needle. In addition, in particular as a result of manufacturing tolerances, in particular of syringes made of glass, in some circumstances it may be difficult, in the stored position, to guarantee sealing between the deformable inner body of the needle guard and the injection device, specifically the syringe body made of glass. In addition, manufacturing and assembling the needle guard, and in particular assembling the outer body on the inner body, may be complex and thus costly. In addition, even if the needle guard is effective in its stored position, it does not make it possible to prevent or avoid any risk of injury from the needle after using the injection device.